Osiris (Greek language, also Osiris; the Egyptian language name is variously transliterated Asar, Aser, Ausar, Ausir, Wesir, or Ausare) is the Egyptian god of life, death, and fertility. He is one of the oldest gods for whom records have been found and first appears in the Pyramid Texts around 2400 BCE, when his cult is already well established. He was widely worshiped until the forcible suppression of paganism in the Christian era. Osiris was not only the redeemer and merciful judge of the dead in the afterlife, but also the underworld agency that granted all life, including sprouting vegetation and the fertile flooding of the Nile River. The Kings of Egypt were associated with Osiris in death such that as Osiris rose from the dead so would they, in union with him, inherit eternal life through a process of imitative magic. By the New Kingdom all people, not just pharaohs, were believed to be associated with Osiris at death if they incurred the costs of the assimilation rituals.

Osiris is the oldest son of the Earth god, Geb, and the sky goddess, Nut as well as being brother and husband of Isis, with Horus being considered his posthumously begotten son. He is usually depicted as a green-skinned pharaoh wearing the Atef crown, a form of the white crown of upper Egypt with a plume of feathers to either side. Typically he is also depicted holding the crook and flail which signify divine authority in Egyptian kings, but which were originally unique to Osiris and his own origin-gods (see below), and his feet and lower body are wrapped, as though already partly mummified. The information we have on the myths of Osiris is derived from allusions contained in the pyramid texts, and, much later, in narrative style from the writings of Plutarch and Diodorus Siculus.

The Original Promo Egyptian God cards are illegal to use in any and all real duels (both Traditional and Advanced Format alike), and they also have no effects, but they can be used in The Sacred Cards, Nightmare Troubadour, Spirit Caller, Tag Force 2, 3, 4 and 5 (via UMD recognition) 5D's Stardust Accelerator, 5D's Reverse of Arcadia and 5D's Over the Nexus.

Yu-Gi-Oh! Anime:Slifer the Sky Dragon
DIVINE/Divine Beast/10/?/?
You must offer 3 Tributes to Special Summon this card. The ATK and DEF of this card becomes the number of cards in your hand × 1000. When this card is Special Summoned from the graveyard, it is sent to the Graveyard during the End Phase. While this card is face-up on the field, it cannot be targeted by Spells, Traps, or Monsters that designate a target. Additionally, when your opponent successfully Summons a monster 2000 points is deducted from the Monsters ATK or DEF respective to its position. If this effect reduces the amount to 0 or less the monster is destroyed.*Further research compiled from both what has been stated in the Anime/Manga and video games, has yielded what I've placed below as the determined powers Slifer possesses in his entirety.
Slifer the Sky Dragon
DIVINE/Divine Beast/10/X000/X000
This card cannot be Set. This card can only be Tribute Summoned by Tributing 3 monsters. The Normal Summon of this card cannot be negated. When this card is Normal Summoned, Spells, Traps, and Effect Monster effects cannot be activated. While this card is on the field, control of this card cannot switch and the card is unaffected by the effects of Trap Cards and Effect Monsters other than “Obelisk the Tormentor” and “The Winged Dragon of Ra”. The effect of “Obelisk the Tormentor” only affects this card for one turn. The effects of Spell Cards only affect this card for one turn. This card cannot be removed from the field by the effects of Spell Cards. This card’s ATK and DEF are equal to 1000x the number of cards you have in your hand. When a monster is summoned to your opponent’s side of the field in Attack or Defense Position, decrease its respective ATK or DEF by 2000. If this reduces that card’s ATK or DEF to 0, destroy that card.==Videogame effectsBewerken==
One of the three Egyptian God Cards, Slifer the Sky Dragon is unusual in that it's flavor text is printed as it's "effect". Despite this obstacle, however, effects have been given to it in its videogame appearances. Slifer was also released in the 7th Japanese Booster of Yu-Gi-Oh! Dungeon Dice Monsters.